Program Project(671PP): Mechanisms of Airway Inflammation. Mild asthmatics who develop a late asthmatic response to an allergen inhalational challenge will be studied. Each subject will undergo two bronchoscopic procedures, one for instillation of allergen and diluent and one for performing the biopsies, brushings, and bronchoalveolar lavage. Equal number of subjects will undergo bronchoscopy at 6 and 24 hours post challenge.